Recently, an apparatus and system for carrying out communication and measuring the distance using pulse signals are under development, as one of techniques utilizing UWE (Ultra Wide Band). Methods of making a pulse signal an alternating current signal having only components of a desired frequency band, include intermittently carrying out oscillation by operating the oscillation circuit which is the alternating current signal source.
FIG. 1 shows a main configuration of a pulse modulation circuit that operates an oscillation circuit intermittently (see Patent Document 1). Pulse modulation circuit 10 shown in FIG. 1 is mainly divided into two parts of short pulse control generation circuit 11 that generates a pulse control signal and oscillation circuit 12 that carries out oscillation during the period of a short pulse. An input signal that determines the intermittent operation cycle is divided into two signals by distribution circuit 21 composed of resistances in short pulse control generation circuit 11, and one signal is inputted to the base terminal of transistor 23 as is and the other signal is delayed by a predetermined period in delay circuit 22 and then inputted to the emitter terminal of transistor 23.
By this means, a short pulse control signal that is shorter by a period matching the delay in delay circuit 22 than the input signal inputted to the base terminal of transistor 23, is generated. The short pulse control signal is inputted to oscillation circuit 12 and makes the oscillator composed of feedback circuit 32 and transistor 33 intermittently operate. Further, in FIGS. 1, 31 and 34 are amplifiers and 35 is the current source.
Further, Non-Patent Document 1 discloses a technique of making a pair of oscillation circuits perform a differential operation. FIG. 2 shows the configuration.    Patent Document 1: Japanese Patent Application Laid-Open No. 2005-49200    Non-Patent Document 1: “Residual-carrier-free burst oscillator for automotive UWB radar applications,” ELECTRONICS LETTERS, Apr. 28, 2005, Vol. 41 No. 9